Telegraphy.



No. 7|l,943. Patented Oct. 28, I902.

A, C. CBEHOBE.

T E L E G R A P H Y (Application filed Mar. 8, 1902.)

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A. C.'CREHUBE.

TELEGBAPHY.

(Application filed Mar. 8, 1902.)

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TELEGRAPHY;

(Application filed. Mar. 5,1902.)

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Patented Oct. 28, I902.

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nv'enidr UNITED STATES PATENT OFFICE.

ALBERT O. CREHORE, OF TARRYTOl/VN, NEWV YORK.

TELEGRAPHY.

SPECIFICATION forming part of Letters Patent No. 711,943, dated October 28, 1902.

Application filed March 8, 1902.

To all whont it may concern:

Be it known that'I, ALBERT O. CREHORE, a citizen of the United States, and a resident of Tarrytown, in the county of \Vestchesterand State of New York, have invented certain new and useful Improvements in Telegraphy, of which the following is a specification.

My invention relates to that class of telegraph apparatus known as superposed-current systems wherein one class or set of messages or signals is sent over a wire by. the use of momentary currents of short duration and sharply defined or having a high rate of change of electromotive force, while another set of signals or messages is sent over the same wire or circuit by currents of longer duration or having a lower rate of change and upon which the momentary currents are superposed.

My invention has reference more particu-,

larly to the systems described in my prior applications, Serial Nos. 79,383, 79,384, 79,385, 79,386, and 79,387, filed October 21, 1901, and to combinations and arrangements of devices especially useful in connection with the inventions described in said applications.

WVith the frequencies of alternating cur-- rent and strengths of current which it is do sirable to employin my prior system disturbances may arise from the inductive effect of such currents upon neighboring telephonelines. Moreover, if the attempt be made to remedy this difficulty by using lower frequencies and less currents there is a liability to interference between the two sides of the system itself, or, in other words, it is difficult to find suitable values for the apparatus which will prevent interference between the two sides of the system itself when employing the desired frequency and currents. My present invention is designed to overcome these difficulties.

Another object of my invention is to permit two separate parties, each on a single Morse wire, to communicate independently with distant stations over a single main-line wire operated as a superposed telegraph-circuit by the use of suitable repeating apparatus.

My invention consists in the combinations of devices and arrangements and connections Serial No. 97,246. (No model.)

paratus embodying my invention at one end.

of a superposed telegraph circuit. Fig. 2 illustrates an arrangementof repeating apparatus embodying my invention and details thereof. Figs. 3, 4, and 5, represent modifications.

Referring to Fig. 1, the main-line circuit enters at A, passes through the receiver set to B, and thence through the alternating-current transmitter set to C, and thence through the direct-current transmitter set to the earth E. The receiving set between the points A and B contains two branches, dividing at A to the points D and F, the alternating currents passing into the apex F and the direct currents passing into the apex D.

The first part of my invention relates to the branch which contains the alternating-current receiver and consists, substantially, in subdividing said branch into two branches unbalanced as to inductance, the receiver being properly connected to said branches, so as to be affected or operated upon by the pulsatory currents through the want of balance in said branches, said receiver being, however, neutral with respect to the variable currents caused by the action of the continuouscurrent side of the apparatus, for which purpose said receiver may be connected into or to said branches inany of the ways known in telegraphy for rendering a receiving instrument unresponsive to currents flowing in two circuits or branches at once. By preference I use the differential method for securing this resultthat is to say, I wind a receiver with two coils serving to neutralize one anothers effects when currents of equal amount traverse them.

Referring to Fig. 1, the circuit divides at E into two branches, each containing a condenser 1 and 2 and each containing one coil of a differential polarized relay 3 4. These two branches are similar in all respects except that one of them is given a superior inductance to the other in any desired manner. A convenient way of effecting this is to insert a separate ind uctancecoil 5 in one of the branches-as, for instance,in the branch including condenser 1. Thence the circuits from 5 and 4 unite at the point B. The coils of the polar relay 3 4 are so connected that equal currents passing from A toward ]3 through the two branches opposes and no magnetism is developed in the relay, the armature remaining still. By inserting the coil 5 the branches become unbalanced and more alternating current flows from F through branch 2 4 than through branch 1 3 5, and this causes action uponthe relay. Moreover, the values of the quantities in this divided circuit are so proportioned that it is found to be the case that more current actually flows through coil 4 of the relay than enters from the main line at F. This is due to a kind of resonant action set up in the 10- cal circuit 1, 2, 4, 5, and 3, and, moreover, all current which passes around this circuit in the order named has the efiect of increasing the action of the relay, for this current passes through its coils in the direction to assist the action. No disadvantage, therefore, from the standpoint of losing in alternating-current eifect is experienced by this arrangement of apparatus; but a great advantage is obtained of almost completely eliminating the disturbances which occur with other dispositions of apparatus, due to the making and breaking or variations in the Morse current, which is simultaneously flowing in the line A, B, O, and E. These Morse currents ordinarily give rise to sudden impulses or kicks, which are noticed in the alternating-cu rrent relay; but these are eliminated in the present apparatus, because these discharges or sudden variations in current divide equally, or nearly so, in the two branches 1 3 5 and 2 4. It is found that the resistance of the coil 5 must be kept small, (in practice ten to fifteen ohms might be permitted,) so that for the discharge the two branches are nearly equal. The other path from A to the point D divides again in two branches, one through 7 and 10 to B and the other through 6, 8, and 10 to B. Coils7and '8 are the two coils of a difierential relay, (either neutral or polar,) and 6 isacondenser having a high non-inductive resistance-shunt 9 around it, and 10 is an inductance-coil, the purpose of which is to partially prevent the alternating current from entering the apex D at all. The direct current has an uninterrupted path from A to E through 7'and 10 to B and thence to earth at E through the alternating-current transmitter set and directcurrent transmitter set. The relay 7 8 will therefore respond to the Morse currents, bedause the effect of these currents is only felt in one coil 7, none of the current passing through the coil 8 except the small amount which is admitted through the high-resistance shunt 9. The small amount of alternating current which does pass through the coil 10 divides equally, or approximately so, in these two branches 7 and 8 and has an imperceptible efiect upon the relay7 '8, because the condenser 6 forms about as good a path for the alternating current as the wire from D to .7. The shunt 9 is provided to prevent slight disturbances in this relay7 8 from the action of the alternating-current transmitter, which has a tendency to set up slight oscillations in the circuits 6 7 8. This shunt is found to prevent these disturbances and is of very small efiect in reducing the strength of the action of the relay 7 8 for Morse currents.

The above arrangement of receiving apparatus is extremely free from disturbance or interference of any kind on either side from the transmitter on the opposite side, and so much so that in manycases it is not necessary to employ so great refinement. In many cases it would do to substitute a Morse relay, as indicated at 71, Fig. 3, in place of the entire receiving set on the direct-current side from A to B, or, as in Fig. 4, an arrangement more free from disturbance on the Morse side than Fig. 3, an inductance-c0il10 may be employed in series with the Morse relay corresponding to 10 in Fig. 1.

The alternating-current transmitter between the points B and Cof the main line consists of an ordinary pole-changing transmitter operated by a Morse key in a local circuit. The generator 'is represented at 11. 12 and 13 represent protective resistances,which prevent the generator from being short-circuited accidentally by the transmitter. 14 represents a resistance connected from a point of the transmitter to a point of the receiver-circuit in the branch 1, 3, 5 between the relay-coil 3 and inductance'coil 5. The purpose of this resistance 14 is to place a shunt around the coil 5, so as to partially short-circuit it during the transmission of a signal'by the transmitter 15 in order that the alternating-cu rrent relay 3 4 may be operated by currents of approximately the same magnitude for outgoing as for incoming or received currents. It will be remembered that the alternating current received at the far end of a line is very much less than the current at the transmitting end of the line, due to the capacity of the line and the leakage. The path for the Morse currents is then from B to 16 and thence through resistance 12 to 11 and thence to the main line C when the transmitter is not in operation, or when the transmitter is in operation the alternative path is from B to 18 and thence through resistance 13 and generator 11 to C. It will be noticed that the transmitter is continuity preserving and the Morse circuit is never interrupted. The normal position of the tongue T when in operation is down, as shown. At such times the terminal of coil 14 is entirely insulated or disconnected and the alternatingcurrent receiver 3 4 is ready to receive messages from the distant end. When the alternating-current transmitter is used,the tongue T first moves upward, allowing the points 14 and 15 to come together and also the circuits 18 and B to be closed, which, in efiect, places the shunt 14 directly around the coil 5, and thus reduces the intensity of the action of the outgoing alternating current on the relay 3 4. The path for the Morse currents continues from C through the Morse transmitting set to earth at E. The transmitter is represented at 24 of the circuit-continuity-preserving'type. The Morse current passes through a retardation-coil 21 and thence to the spring of the transmitter 25 and normally to earth, at E, through the protective resistance 22. If the transmitter is working, the alternative path is through coil 21 to the spring 25 and stop 26 of the transmitter, through the protective resistance 23 and direct-current generator 27 to earth. Thus the Morse circuit is never broken, but the electromotive force is removed and inserted by the operation of the transmitter, which is worked by a Morse key on a local circuit. (Notshown.) ApathfromCthrough the inductance-coil 19 and condenser 20 and thence to earth is also provided in order that the alternating currents on the line may have a free path to earth. While this is a preferred arrangement suitable" for some purposes, yet it is not always necessary to employ a'transmitter of the continuity-preserving type, a Morse key being provided, as in Fig. 5, in series with the retardation-coil 21 and the direct-current generator being placed directly in the line. In many cases this retardationcoil 21 is not required at all. These cases are when the Morse line is sufiiciently well loaded with inductance due to a large number of Morse stations; but if a line has only two or three Morse stations it is usually best to employ such a coil. If such a coil is employed, it should be carefully balanced by the coil 19 and condenser 20, so that the opening and closing of the Morse key 29, Fig. 5, will not produce a permanent change in the value of the alternating current in-the relay 3 4, Fig. 1. It is found in practice that such values may be given to the coil 19 and condenser 20 that the opening of the key 29 will cause the received alternating current in relay 3 4, Fig. 1, to increase, or by changing the values of this coil and condenser it may decrease by opening the key. Such values should be used as will not give any perceptible change in the received alternating current. This matter is of particular importance only when the Morse key 29 is employed so as to open that branch of the transmitting set-that is, when the closed-circuit Morse system is used. The use of the continuity-preserving transmitter 24 on the open-circuit system, as in Fig. 1, does away with the necessity for employing such an exact balance.

The system as shown in Fig. 1 is devised for working at comparatively low frequency of alternating current fifty or sixty cycles per second and also for comparativelysmall values of transmitting electromotive force in order that it may be suitable for operation in proximity with telephone-circuits or in conduplex-diplex system, as described in patent I applications, Serial Nos.79,383, 79,384, 79,385, 79,386, and 79,387, filed October 21, 1901, is not permissible on Wires in close proximity with telephone-circuits, because of the extreme sensitiveness of telephones to small alternating currents of this periodicity. The difiiculty of working a duplex-diplex system at a low frequency is very much greater than at the higher frequency. This is partially due to the fact that a very large condenser is not permitted to be employed around an ordinary Morse key, as in Fig. 5. It has been found in practice that a Morse operator can detect the presence of a condenser, as at 20, Fig. 5, of anything over three microfarads. The impedance of so small a condenser as this at the low frequency is very greatlyincreased, and it is'not easy to construct an inductancecoil19 which will balance this condenser without introducing considerable apparent resistance, and thus the total impedance added to the line for alternating currents by a single transmitting set is much greater than it is with the high frequency. Moreover, with the low frequency it is more difficult to differentiate between the Morse current and the alternating current received, which is natural when it is considered that if the frequency is decreased to a very low value it is approximating in character the Morse current itself. The kicks produced on the alternating-current receiver by the operation of the Morse key are caused by currents of a variable character, which produce effects which are more similar to an alternating current of fifty or sixty cycles apparently than they are to one of one hundred and fifty cycles, and for a successful system we must diiferentiate between these sudden effects produced by the Morse key and the alternating current received. The receiving apparatus in Fig. l fulfils this condition of differentiating in a very complete manner.

Fig. 2 represents a repeater set suitable for serving two separate parties with a single Morse wire over a single main-line wire entering the diagram from the left at A and passing to earth E. One party may be served over the two wires at the right-hand upper side of the diagram, called D 0 side, and another party by the wires at the lower righthand side of the diagram, called A 0 side. These parties each employ an ordinary opencircuit Morse key, as at 35, with a back contact, using their own battery to operate the wire as a Morse line. These keys and relays are not represented in the diagram. They are the same for the A 0 side and for the DO side. The arrangement of the receiving and transmitting sets on the main line is substantially that shown in Fig. 1, the circuit enter- IIS ing at A and dividing to the points D, which i is the apex of the direct-current polar relay,

and F the apex of the alternating-current polar relay. The direct current thence passes through relay-coil 7 to the point B through coil 10. The other path from D is through the second coil of the polar relay Sin such direction as to oppose the action of coil 7, and thence to the condenser 6, with shunt 9 uniting at the coil 10, and thence to B on the main line. Following the alternating-current side from A to F, We pass through coil 4 of the alternating-currentrelay and condenser 2 to the point B on one side and on the other through relay-coil 3 and coil 5 and condenser 1 to B. From B we enter the alternatingcurrent transmitter at 16 and protective resistance 12 to one terminal 17 of the alternating-current generator 11, thence to the point C on the main line. From 0 the alternatingcurrent path is through condenser 20 and coil 19 to earth E. The normal position of the tongue T of the alternating-current transmitter 15 is indicated by the arrow in a downward direction, and the lower right hand spring of that transmitter has an insulatingstop which insulates the tongue from the two right-hand contacts. When the alternatingcurrent transmitter is operated, the tongue is first raised and the path of the Morse currents on the main line is then changed to the following: B to the tongue T, to the protective resistance 13, thence through generator 11 and terminal 17 to O on the main line.

The operation of the repeater on the D 0 side may be described as follows: The operator closes his key, connecting in his battery to the line 30, whence the current flows to the middle contact of the pole-changer 31, which is normally on the back-stop 32, and thence through the two neutral relays 33 and 34 (which may be arranged either in series or in parallel) to the middle point of key at 35, which is normally upon its back-stop 36, and thence to the return-circuit 37. This current immediately operates the relay 33, closing the contact at 38, and thus causing the local battery 39 to operate theD C transmitter 24 through the local magnet 40. This transmitter 24 immediately puts the Morse current upon the main line A, passing through the coil 7 of the relay. This relay then closes its contact at 41, which contact normally puts the battery 39 on the magnet 42 of the D C side-linepole-changer; butit is prevented from now acting upon this pole-changer, because the circuit through 42 also passes through the additional contacts 43 on the D C transmitter. The first action of this transmitter is to open this contact 43, and thus render the back action of relay-contacts 41 on the D O transmitter 42 of no efiect. We will now trace the operation when the current is put on at the distant end, so as to enter the station over the main line at A. Its path is through the relay-coil 7 and coil 10 to B and to earth through A G and D G transmitters.

Its first effect is to close the contacts 41 of the main-line D O relay, and since the contacts 43 of the D G transmitter are at this time closed, the contact 41 operates the D O pole-changer 42 by the local battery 39. This changes contact from the back stop 32 to the front stop 43 and completes the circuit through the local battery 44 to the return 37, and thus operates the sounder on'the D 0 side line. Duringthis action the D 0 mainline transmitter 24 remains at rest and the side-line pole-changer 42 responds to the signals from the distant operator on the main line. W hen the side-line operator is Working, the pole-changer 42 remains at rest and the main-line transmitter 24 responds to his signals, transmittingthem to the distant end over the main line. The manual key is merely provided for convenience at the repeater-station. Thus far the purpose and action of the relay 34 have not been described. The Morse working on a line is usually better when the circuit is free from retardation-coils, and only a certain amount of retardation is permitted on a good Morse circuit. It is found that for the successful operation-0t the system the retardation-coil is only required at the station where the Morse transmitter is operating, and when this transmitter is not operating the retardation-coil, and consequently the condenser-shunt around it, may be cut out of the line. This is accomplished by the relay 34 operating to open the contacts 45 when the Morse current is being transmitted and close these contacts, thus shortcircuiting through circuits 45 and 46 the retardation coil 21. In this connection it should be said that the adjustment of this relay 34 must be rendered sluggish, so that it will not respond quickly to dashes, but will respond quickly to (lots. In this way it insures that the short circuit on 21 shall not be present by any possibility when the transmitter 24 is in operation. The operation of the alternating-current side is as follows: When the A C side-line operator closes his key, putting on his battery, the current comes in over the line 47 to the middle point 48 of the pole-changer, which pole-changer normally makes contact on the stop 49 when no currents are passing over the line. The path is then continued through the neutral relay 50 to the return 52 through the back stop 51 of a key 53. The first action of this current is to close the local contacts 54 of relay 50, and this closes the circuit through the local battery 39 and local magnet 55 of the main-line alternating-current transmitter. The tongue T of the transmitter then moves upward, inserting the alternating electrometive force in the main line, which would normally operate the alternating-currentrelay coil 3 4, but in this instance is prevented from doing so because the first thing which the transmitter accomplishes is to close the circuit 15 and 56, thus short-circuiting the inductance-coil 5, which causes the alternating-current receiver-circuits to be in perfect balance for alternating currents, so that coils 3 at oppose each other equally, and thus the contacts 57,which are normally closed,remain so closed,

and are not affected by the outgoing alternating current. No back action upon the transmitter 48 is therefore caused by these contacts 57. When the alternating-current operator at the distant end transmits alternating current over the wire entering at A, the first effect of this is to open the contacts 57, which are normally closed,because the coil 5 is nowinserted in the circuit, contacts 15 and 56 being normally open. The efiect of the opening at 57 is to remove the battery 39 from the polechanger coil 58. This releases the armature and brings the circuit 48 into contact with the stop 5.9,and thus completes the circuit through 59 and 60 and battery 44 to the return 52, putting current upon the relay of the A 0 side -line operator. When the signals are coming from the main line on the alternatingcurrent side,the alternating-current transmi tter 15 is at rest and pole-changer l8 responds to his signals. WVhen the side-line A C operator is working, pole-changer 48 remains at rest and transmitter 15 responds to his signals. The key 53 is merely added for convenience and, like 35, operates in both directions over the side line and main line. One important point in this repeater is the mannerin which the back action upon the transmitter 48 by the relay 3 L is prevented by means of the short-circuiting contacts 15 56. These contacts are insulated from the rest of the transmitter and may therefore be employed to short-circuit any points desired in the system. At first one would imagine that short-circuiting the points 61 and 62, which puts the alternating-current relay into exact balance so that the current in one coil exactly opposes that in the other, would be best. This plan Worked well when the transmitter 15 was closed,but failed to work when the transmitter was opened,because although the alternating current was removed from the line before the short circuit 15 56 was opened, yet there remained in the circuit 1 2 4 3 5 sufiicient current to cause a disturbing elfect upon the contact 57. It is thought that this disturbing action is caused by the coil 5 discharging, and it was found that by short-circuiting this induction-coil 5 instead of the relay the disturbance alluded to was entirely eliminated.

The invention claimed is- 1. In a repeating apparatus for superposedcurrent systems, the combination with the differential relay on the pulsatory-current side and an inductancecoil in one of the branches, of a transmitter and means controlled thereby for taking the said inductance out of circuit to render the repeating-transmitter quiescent, as and for the purpose described.

2. In a repeating apparatus for superposedcurrent systems,a normally short-circuited retardation-coil 21 combined with means for introducing it into circuit only when the Morse transmitter is operating at the same station, as and for the purpose described.

3. In a repeating apparatus for superposedcurrent systems, a normally short-circuited retardation-coil 21 combined with a relay adjusted as described for introducing it into circuit only when the Morse transmitter is operating at the same station, as and for the purpose described.

4:. In a superposed-current telegraph, the combination with a single main line carrying two messages of the two single Morse circuits and means whereby the messages coming from one of the latter may be repeated into the pulsatory-current side of the main line and from the other upon the continuous-current side and vice versa.

5. In a superposed-current telegraph, a receiver for the pulsatory-current side having differential coils in branches of the main line and an inductance-coil (as 5) adapted to unbalance the receiver for alternating currents and to keep it in balance for the variable current caused by the action ofthe continuouscurrent transmitter, as and for the purpose described.

6. In a superposed-current telegraph, a receiver for the pulsatory-current side having differential coils in branches of the main line and an inductance-coil (as 5) adapted to unbalance the receiver for alternating currents, and a condenser in each branch, as and for the purpose described.

7. In a superposed-current telegraph, a receiver for the pulsatory-current side having diiferential coils in branches of the main line and an induction-coil (as 5) adapted to unbalance the receiver for alternating currents, and a continuous-current receiving set in shunt to the pulsatory-current receiving'apparatus, as and for the purpose described.

8. In a superposed-current telegraph, a differential receiver for the continuous-current side having its two coils in branches of the main line respectively, as and for the purpose described.

9. In a superposed-current telegraph, a differential receiver for the continuous-current side having its two coils in branches of the main line respectively, and means (as 6) in one branch adapted to unbalance the relay for continuous currents but to preserve it in balance for alternating currents.

10. In a superposed-current telegraph, a differential receiver for the continuous-current side having its two coils in branches of the main line respectively, an unbalancingcondenser, and a non-inductive shunt around said condenser, as and for the purpose described.

11. In a superposed-current telegraph, a differential receiver for the pulsatory-current side, having its two coils in branches of the main line respectively and an inductance in one of said branches, in combination with a transmitter for the alternating-current side and a resistance controlled thereby and inserted as a shunt around said inductance, as and for the purpose described.

12. In a superposed-current telegraph, the combination with the continuous current transmitter and a retardation-coil in series therewith, of a shunt around said transmitter and coil said shunt containing a condenser and inductance.

13. The combination with the difierential alternating-current receiver having its coils in branches of the main line,of an inductance coil of low resistance and high inductance in one of said branches, as and for the purpose described.

14. In a superposed-current telegraph, the combination with a dilferential pulsatorycurrent receiver provided with an unbalancinginductance,a pulsatory-current generator and transmitter, and means controlled by said transmitter for cutting out said unbalancing inductance during the transmission of a signal, as and for the purpose described.

15. In a superposed-current telegraph, the combination with the receiver for the pulsa tory-current side having differential coils in branches of the main line, a device for unbalancing said branches to the flow of the pulsatory'currents, a shunt around the latter adapted to partially short-circuit it, a pulsatory-current generator, a transmitter and means controlled by said transmitter for closing said shunt.

16. In a superposed current telegraph, a receiver for the pulsatory-current side having difterential coils in branches of the main line unbalanced as to alternating currents.

17. In a superposed-current telegraph, the combination with the pnlsatory-current receiver, of main-line branches connected to said receiver and unbalanced as to alternating currents, as and for the purpose described.

Signed at New York, in the county of New York and State of New York.

ALBERT O. OREHORE. 

